Introduction
Picking the correct developer might be crucial when making smooth, user-friendly iOS apps. This article provides a thorough set of questions that recruiters and hiring managers may use to find the best candidates for the position of iOS developer. The purpose of these questions is to assess the technical knowledge and practical expertise of the candidate you are hiring by testing their ability to comprehend and work inside Apple’s ecosystem and to ensure that the application runs well on various devices.
Choosing a reliable digital transformation partner can also help organizations streamline their hiring process and build efficient iOS solutions.
iOS Interview Questions & Answers
The following sections will help you organize the questions that are most commonly asked during an iOS interview:
1. What is iOS?
One definition of iOS is “iPhone Operating System.” This is the OS that powers all of Apple’s devices, and it’s often regarded as the world’s second most popular mobile OS, right after Android. Numerous Apple devices, such as the iPod, iPad, and iPhone, run on this operating system. The sleek and user-friendly interface of iOS has garnered a lot of praise.
2. What are the features of iOS?
iOS has grown in popularity due to its many useful features. Some of its most appealing qualities are as follows:
- You can multitask on an iPhone. The multitasking function or a multi-finger motion makes it easy to switch between applications on an iOS device.
- The activity stream and content sharing features in iOS make it easy to incorporate social network interactions into your app.
- Users are able to save data online with Apple’s iCloud service. To protect user data from loss, it provides a backup option and uses a high level of encryption.
- You can buy digital things (iOS, iPad, macOS), subscriptions, and premium content through Apple’s in-app purchases, which are accessible on all platforms.
- Notification Center is where you can view all of your app alerts on iOS. It is possible to change the notification settings, though.
- The iOS ecosystem is closed. No one can access the source code of Apple’s apps, and even fewer people can make changes to the code on their own iPhones or iPads. As a result, smartphones running iOS are more difficult to hack.
3. Can you explain CoreData?
To manage object graphs, CoreData is a useful framework for iphone software development company. It is useful for managing a potentially massive graph of object instances. As a result, the program may make use of a graph that wouldn’t fit entirely in memory by retrieving objects from memory as needed. Managing restrictions on properties and relationships and ensuring reference integrity are two other areas where CoreData is useful. What this means is that the forward and backward links in a relationship don’t change when objects are added or withdrawn. A perfect framework for building the “model” of an MVC architecture is thus thought to be CoreData.
4. How are “copy” and “retain” different?
In most cases, the retain count of an object is raised by one whenever it is retained. It helps in remembering the object rather than getting completely swept away by it. Consequently, you will reciprocate the favor with the sender of an item if you own only the retained form of it.
On the flip side, when you copy anything, you make a second copy of it. You should not give the sender a duplicate or copy of the item; instead, you should keep the original and share it with them.
5. How can one accomplish concurrency on iOS?
“Running multiple tasks simultaneously” is what we mean when we talk about concurrency. Thanks to concurrency, iOS devices can keep the user interface responsive even while they analyze data or download files in the background. Grand Central Dispatch (GCD) and Operations (formerly NSOperation) are two methods for managing tasks in iOS that are running at the same time. Here are three ways that iOS allows us to accomplish concurrency:
- Dispatch queues: You can use them to organize jobs in FIFO order and perform them sequentially or simultaneously. In your application, this is a simple method to manage both concurrent and asynchronous (not happening at the same time) tasks.
- Threads: The execution of one set of instructions does not depend on the execution of any other code in the program. Threads allow for the simultaneous execution of numerous code paths within a single program. When you need to do a long task independently of the rest of the application, a thread is your best bet.
- Operation Queues: The availability and priority of the operation queue objects determine how they are invoked. Operation queues are essentially GCD (Grand Central Dispatch) based abstractions of queueing architectures. Thus, it is feasible to run jobs in parallel, similar to GCD, but with an object-oriented approach.
6. What do you understand by iOS app code signing?
In addition to verifying that the applicant did not make any subsequent edits to the application, a signed application tells the system who signed it. Doing so is essential before submitting the app to the Mac and iOS App Stores. Both OS X and iOS have signature verification processes to make sure apps can’t run with fake signatures. Users may rest assured that the software has not been modified since it was signed by a verified Apple Source, which adds trust for them.
Xcode uses your digital identity to digitally sign your program while it is being built. A digital identity consists of a certificate and a set of public and private keys. To generate the signature, the cryptographic functions consult the private key. A certificate including the public key and aiding in identifying you as the owner of the key pair is issued by Apple.
The signature safeguards the application’s executable code since it becomes invalid upon any modification, no matter how small, to the application’s executable code. The signatures remain valid even after editing photos or nib files, since these resources are not signed.
A new digital identity can be used to re-sign an application once its signature has been deleted. When you buy an app from the App Store, for instance, Apple re-signs it.
It would be helpful to provide any relevant work experience you may have had with code-signing for iOS apps as a response to this type of iOS interview question.
7. Can you explain MVC?
A model-view-controller is abbreviated as MVC. When creating apps for iOS, it is the primary software design pattern used by Apple. The application’s data is represented via models. Views make things visible on the screen. To control how information moves from the model to the view, developers utilize controllers. The controller handles all communication instead of the model and view communicating directly.
While Model-View-Controller (MVC) is useful for general-purpose design, it is limited to the view layer, which a senior developer should be aware of. Because of this, limiting oneself to MVC will limit the application’s architecture and may even cause the “Massive View Controller” issue.
When View Controllers are overwhelmed with logic and responsibilities that they aren’t designed to handle, the result is a massive view controller in the codebase. Because of this, the code could end up being too thick, unmanageable, and hard to change. Design patterns like Coordinator, MVP, and MVVM can be used as a solution. Use VIPER and RIBs, for example, to scale the iOS code and sidestep this kind of issue.
8. What is the language used to create for iOS?
When creating an iOS app, Swift is the language of choice. Objective-C is also utilized, while Swift has been gaining more and more traction.
9. Describe overlays.
An operating system technology called an overlay allows programs to use more memory than they would be able to use without the overlay.
A specific amount of space is consumed when an app is loaded into memory. Overlays allow you to load just the parts of the program that need to be put into memory, which is useful when dealing with huge programs that demand more memory than what is available. Parts of the program can be moved about in memory as needed while it runs.
10. Explain the bounding box.
One way to depict an object or shape is with a bounding box, which is a tiny rectangle that covers it entirely. The object on the screen can be anything from a picture to a text character. Its size and location establish the bounding box. The width and height of the rectangle define its size, while the coordinates of the top-left corner define its position.
11. NSUserDefaults: What is it?
The use of key-value pairs is the most basic form of data storage that does not use a database. Its primary function is to facilitate communication between the default systems and programs. This is the default setting that allows applications to adapt their behavior to the user’s preferences. Users have the option to choose their preferred media playback speed, for instance.
12. Can an extension be used to add a stored value to a type?
In Swift, it is not possible to extend a type with a stored property. Adding stored properties to a type is not possible with Swift extensions; however, instance methods, class methods, initializers, and calculated properties can be added. The reason behind this is that extensions are unable to provide their own initializers, which means that stored properties cannot be loaded when a type instance is generated.
13. Which JSON framework is compatible with iOS?
The SBJson framework is a simple and straightforward data interchange standard. In this case, JSON refers to JavaScript Object Notation. This Objective-C tool simplifies JSON processing with its built-in syntax analyzer and generator, which also offers more controls and adaptable APIs. The SBJson framework allows you to perform things like start parsing and return chunks of the parsed page, lower the apparent latency for every downloading and parsing cycle of files over a sluggish connection, and parse big texts bit by bit instead of keeping them in memory.
14. Explain what each of iOS’s Process States is.
- Not Running: The program is either never launched or was running when the system terminated it.
- Inactive: Although it is not getting any events, the app remains in the foreground. As apps move to different states, this one is usually short-lived.
- Active: As it receives events, the app remains in the foreground.
- Background: The app is running code in the background. This is a temporary state that most apps go through before getting suspended.
- Suspended: There is no code execution happening while the app is in the background. To free up memory for other applications, the system may unintentionally remove suspended ones from memory at any moment.
15. Are you familiar with iOS’s Grand Central Dispatch?
One low-level API that enables parallel task execution is Grand Central Dispatch (GCD). It handles background thread management as well. It includes language extensions, system upgrades, and runtime libraries that make iOS multicore hardware better in every way.
16. How would you recommend storing data in memory cache?
Even though there are a lot of options, NSCache is better than a basic dictionary since it clears the cache automatically when memory is low. Without your knowledge or consent, NSCache will intelligently remove items from cache while attempting to retain as much as possible.
In addition to these features, NSCache also supports arbitrary keys and values, thread-safe access to cached data, and delegate methods that allow you to customize the behavior. Because of these characteristics, NSCache is a caching solution that is both versatile and strong enough to handle a variety of tasks.
Conclusion
Everywhere you look, people are using Apple products. This bodes well for the makers of iOS apps, as the number of iOS users throughout the world has been increasing consistently.
To help you ace your iOS job interview, we have compiled a list of the questions that are most often asked. It is important for iOS developers to keep up with community news and developments. You should also subscribe to podcasts, read blogs, and keep up with Apple developer news. Best of luck!
